The present inventions relate to belts and belt lubricants, and more particularly to lubricated, endless belts for treadmills.
Treadmills used for exercise are well known and very popular. A prior art exercise treadmill typically includes an endless belt that is driven by a motor so that the bottom surface of an upper run of the belt slides across an upper surface of a stationary deck. In use, a person using the treadmill engages the top surface of the upper run of the belt at a position above the deck, which contributes to friction between the bottom surface of the upper run and the upper surface of the deck. Over the years, efforts have been made to reduce this friction, in an effort to reduce: the power required to drive the belt, friction-induced heating, and friction-induced noise. Reducing the friction can enhance the operation and life of the belt. It is known to reduce the friction between treadmill belts and decks through the use of lubrication, and there are several known lubricants and associated methods.
It is prior art to apply a lubricant, such as a lubricant consisting of polypropylene wax, a polyurethane binder and solvent, to rolls of belt material before forming endless belts (e.g., “light duty” belts, which are discussed below in this Background section) from the belt material. Then, the solvent is driven off by heating, so that the resultant lubricant is impregnated in the belt material and is substantially in solid form at room temperature. Thereafter, sections are cut from the belt material and joined (e.g., spliced) end-to-end to form the endless belts that are used as treadmill belts. Although the foregoing method of lubricating is very efficient in some regards, it can only be used with limited types of lubricants, because some lubricants will interfere with the splicing.
It is prior art to apply a liquid silicone lubricant to the bottom surface of an endless treadmill belt. When using a liquid silicone lubricant, the lubricant is typically individually sprayed or rolled onto individual treadmill belts after the treadmill belts have been formed/made endless. According to one prior art method, an endless belt is placed on a lubricating fixture having three rollers that the belt extends around such that the “bottom” (i.e., “inner”) surface of the belt engages the pulleys and the “top” (i.e., “outer”) surface of the belt faces away from the pulleys. One of pulleys is driven and an applicator applies the silicone lubricant to the bottom surface as the belt travels relative to the applicator.
The liquid silicone provides adequate lubrication, but since it remains in liquid form, it has a tendency to migrate to the top surface of the belt, to any packaging materials used when shipping the belt, or to other locations where lubrication is not desired. Additionally, if too much silicone liquid is applied, belt tracking problems can result, meaning that the belt can become misaligned around the pulleys of the treadmill. If too little silicone liquid is used, belts are inadequately lubricated, which can disadvantageously increase the amount of power required to drive the belt, as well as the heat and noise generated by the belt sliding across the deck, which can negatively impact the life and operation of the belt. Finally, lubricating endless belts individually is slow and labor intensive compared with coating rolls of belting prior to forming endless belts therefrom. Typically, liquid silicone cannot be efficiently applied to rolls of belting before making numerous endless belts therefrom because the liquid silicone will interfere with bonding/adhesion that is necessary for satisfactorily splicing.
It is also prior art to apply wax to the upper surface of the deck of a treadmill. The wax can provide adequate lubrication only if a sufficient quantity is used. If too much is used, wax clings to treadmill rollers resulting in excessive noise and tracking difficulties. After a period of use, wax is typically lost from the deck such that some form of relubrication is necessary. As one example, U.S. Pat. No. 3,659,845 discloses a treadmill with a stationary support surface over which the upper run of a belt travels, and the upper surface of the support surface is formed from canvas that is impregnated with a wax, such as carnauba wax.
Whether or not a lubricant is used, the underlying construction of a treadmill belt can also affect the amount of friction resulting from the treadmill belt sliding across the deck. For example, a prior art “light-duty” treadmill belt, which is particularly well suited for use in homes, will now be described. The light-duty belt has all polyester top and bottom plies that are joined by an adhesive (e.g., polyurethane or PVC) positioned between the top and bottom plies. The top ply is a plain weave of 1000 denier multifilament polyester yarns, and the bottom ply, which includes the bottom surface that slides across the deck, is a plain weave, with both weft and warp yarns being spun polyester yarns formed from staple fibers. This “light-duty” belt is formed by cutting a section from a roll of belt material after the belt material has been lubricated as described above, so that the bottom surface of the bottom ply of the belt is impregnated with a lubricant mixture of polypropylene wax and polyurethane binder. The endless belt is formed by splicing the opposite ends of the cut section together. The splice is a “Z” splice, meaning that opposite ends of the section are cut in a zigzag pattern and then meshed together, with a PVC strip hot-pressed at the meshed area, over the top surface of the top ply.
As an additional example, a prior art “heavy-duty” treadmill belt, which is particularly well suited for use in spas, will now be described. The heavy-duty belt has all polyester top and bottom plies that are joined by an adhesive (e.g., polyurethane or PVC) positioned between the top and bottom plies. The top ply is a plain weave of 1000 denier multifilament polyester yarns. In the bottom ply of these belts, the weft yarns, which extend across the belt, are monofilament, and warp yarns, which extend in the longitudinal direction (i.e., the direction of belt travel), are 1000 denier multifilament polyester yarns (i.e., “continuous” filament yarns). Plain weaves as well as twill weaves (e.g., 3/1) are used for the bottom ply. In the twill bottom plies, the long, floating portions of the warp yarns contact the deck that the belt slides across, with the belt traveling in the longitudinal direction in which the warp yarns extend. Likewise, the belt travels in the longitudinal direction in which the warp yarns extend for the plain weaves. In these belts, the warp yarns are twisted about 130 turns/meter. For this “heavy-duty” belt, it is formed by cutting a section from a roll of belt material and forming a continuous belt via splicing the opposite ends of the section together. The splice is formed by peeling back plies at the opposite ends and then overlapping and sealing together those overlapped portions. This type of belt is typically run on a waxed deck or otherwise used in a treadmill with an automatic lubricating system that sprays lubricant onto the belt during use of the treadmill.
Although prior treadmill belts operate reasonably well, there is always a desire for new treadmill belts that provide an improved balance of properties.